Asymmetric Distribution of Ribosomes in Escherichia coli Cells Reveals Insights into Bacterial Aging

핵심 개념

The asymmetric distribution of ribosomes between old and new daughter cells of Escherichia coli is a fundamental upstream process that contributes to the phenomenon of bacterial aging.

초록

The study examines the spatial and temporal distribution of ribosomes in single Escherichia coli cells to gain insights into the process of bacterial aging. Key findings:

1. New daughters at birth have higher ribosome density compared to old daughters, especially when the daughters are from old mothers.

2. The asymmetry in ribosome distribution between old and new daughters is already present in the mother cells before division, suggesting that the placement of ribosomes in the mother sets up the ribosome asymmetry in the daughters.

3. The variance in ribosome density and elongation rates has both stochastic and deterministic components, with the deterministic component being higher in daughters from old mothers.

4. The spatial distribution of ribosomes within mother cells changes over time, with ribosomes accumulating more in the regions that will become the new poles of the daughter cells.

5. The reduced ribosome density in old daughters could be quantitatively accounted for by the volume occupied by protein aggregates, suggesting competition for space between ribosomes and aggregates as a potential mechanism underlying bacterial aging.

The results indicate that the asymmetric distribution of ribosomes, a fundamental cellular process, is a key contributor to the phenomenon of bacterial aging, going beyond previous observations of asymmetries in expressed gene products and protein aggregates.

통계

The elongation rate for new daughters was 2.148 hr^-1 and for old daughters was 1.964 hr^-1.
The proportional reduction of ribosomes in the old daughter relative to the new daughter was 0.0764.
The volume needed to reduce the elongation rate of the old daughter to 1.964 hr^-1 was estimated to be 0.0603 μm^3.
The largest protein aggregates had a mean volume of 0.0852 μm^3.

인용구

"The asymmetry creates fitness variance between daughters that increases the effectiveness of natural selection (2, 15), and an asymmetrical lineage has more progeny over time relative to a symmetrical one."
"Because damage aggregates also tend to reside at the poles (7), we need to evaluate whether the volume of added aggregates displaced a volume of ribosomes that could quantitatively account for the elongation rate difference between old and new daughters from old mothers (Fig. 2C)."
"Until new studies prove otherwise, we believe that the elongation rate and aggregate correlations of Lindner et al. and Govers et al. should be viewed as alternative models to be further tested."

핵심 통찰 요약

Spatial and temporal distribution of ribosomes in single cells reveals aging differences between old and new daughters of Escherichia coli

by Chao,L., Che... 게시일 www.biorxiv.org 06-23-2023

https://www.biorxiv.org/content/10.1101/2023.06.21.545935v1

더 깊은 질문

How do the mechanisms underlying the asymmetric distribution of ribosomes in E. coli relate to the asymmetric partitioning of other cellular components, such as damaged proteins and expressed gene products?

The asymmetric distribution of ribosomes in E. coli is interconnected with the asymmetric partitioning of other cellular components like damaged proteins and expressed gene products. The asymmetry observed in ribosomes, damaged proteins, and gene products is a result of the division process in E. coli, where a mother cell produces daughters with different characteristics. This asymmetry is crucial for the survival and fitness of the bacterial lineage.
The mechanisms underlying the distribution of ribosomes, damaged proteins, and gene products are intertwined. The slower daughter cell, referred to as the old daughter, tends to inherit more damaged proteins and fewer expressed gene products compared to the faster daughter, known as the new daughter. This asymmetry is a result of the partitioning of cellular components during cell division, where the mother cell segregates these components unequally to its daughters. The old daughter, inheriting more damaged proteins, experiences a decline in elongation rate, which is a form of bacterial aging.
The relationship between ribosomes, damaged proteins, and gene products is significant because ribosomes play a central role in protein synthesis, and their distribution affects the overall cellular metabolism. The asymmetrical distribution of these components reflects the cellular aging process in E. coli, where the accumulation of damage and the decline in protein synthesis contribute to the aging phenotype observed in the old daughters. Understanding these mechanisms provides insights into how cellular components are partitioned asymmetrically and how this impacts bacterial aging.

How do the potential evolutionary advantages and disadvantages of the asymmetric distribution of ribosomes in E. coli relate to the concept of bacterial aging?

The asymmetric distribution of ribosomes in E. coli presents both evolutionary advantages and disadvantages in the context of bacterial aging. The asymmetry observed in ribosomes between old and new daughters contributes to the physiological aging of the bacterial lineage.
One potential evolutionary advantage of this asymmetry is the increased fitness variance between daughters, which enhances the effectiveness of natural selection. The asymmetry creates a scenario where the faster daughter has a competitive edge in growth and reproduction, leading to a higher reproductive success rate. This asymmetry allows for the lineage to adapt to changing environmental conditions and increases the overall survival chances of the population.
However, there are also disadvantages associated with the asymmetric distribution of ribosomes. The slower daughter, which inherits fewer ribosomes, is more susceptible to damage accumulation and reduced protein synthesis, leading to a decline in growth rate and potential cell death. This asymmetry can limit the longevity and viability of the old daughter lineage, especially under stressful conditions where damage accumulates rapidly.
The concept of bacterial aging is closely linked to the asymmetric distribution of ribosomes because it highlights how cellular processes such as protein synthesis and damage repair contribute to the aging phenotype. The asymmetry in ribosomes reflects the physiological changes that occur in aging cells, where the decline in cellular functions leads to reduced fitness and survival. By studying the evolutionary implications of ribosomal distribution in E. coli, we can gain a better understanding of how bacterial aging influences the dynamics of microbial populations.

Could the insights gained from studying ribosomal asymmetry in E. coli provide broader implications for understanding the origins of biological aging in more complex organisms?

Studying ribosomal asymmetry in E. coli can indeed provide broader implications for understanding the origins of biological aging in more complex organisms. The mechanisms underlying ribosomal distribution and its impact on cellular function and aging in E. coli can offer valuable insights into the aging processes of higher organisms, including humans.
The asymmetrical distribution of ribosomes in E. coli reflects fundamental principles of cellular organization and function that are conserved across different species. Ribosomes play a central role in protein synthesis, a process essential for cell growth, maintenance, and repair. The asymmetry observed in ribosomal abundance between old and new daughters highlights how cellular components are partitioned asymmetrically during cell division, leading to differences in cellular function and aging.
By extrapolating the findings from E. coli to more complex organisms, we can gain a better understanding of how cellular asymmetry and aging are interconnected. The evolutionary implications of ribosomal asymmetry in bacterial aging can shed light on the origins of biological aging in multicellular organisms. The insights gained from studying ribosomal dynamics and aging in E. coli can provide a foundation for exploring similar processes in higher organisms and how they contribute to the aging phenotype observed in complex biological systems.